In membrane tank technology, the internal surfaces of a supporting structure such as the internal hull of a ship having a double hull or a shore-based storage facility are covered with a multi-layer structure containing two fine sealing membranes alternated with two layers of thermal insulation, which serve both to limit the flow of heat through the tank wall and to support the fluid-tight membranes structurally.
In order to maximize the operating performance of a suchlike tank, it is desirable to optimize the useful storage volume that it is possible to load in the tank and to unload from the tank. However, the use of an unloading pump which sucks the liquid towards the top of the tank makes it necessary to maintain a certain liquid level in the bottom of the tank, as the suction element of the pump will otherwise enter into communication with the gaseous phase, which will deactivate and/or degrade the pump. Taking account of the specific circumstances which may arise during the operation of the tank, for example under the effect of sloshing of the load caused by wave action or by an earthquake, the necessary liquid level can be minimized only with difficulty.
Publication JP2001108198 envisages the provision of a localized depression in a bottom wall of a shore-based tank exhibiting reduced dimensions with respect to said bottom tank wall. A suchlike depression constitutes a buffer reservoir known as a sump, into which the pumping pipe discharges. More specifically, the pumping pipe is secured to a lateral wall of the tank such that its bottom end is inserted into the sump. The dimensions of the sump and the insertion of the end of the pumping pipe into the sump thus enable the quantity of liquid necessary for the effective functioning of the pump to be limited and optimizes the operating performance of the tank.
However, the lower end of the pumping pipe is left loose in the sump. As a result, this end of the pumping pipe is able to behave like a pendulum in the case of a heavy swell for a tank installed in a ship or else an earthquake in the case of a tank housed in a shore-based facility. Furthermore, this free end of the pumping pipe may exhibit undesirable and repetitive movements as a result of oscillations caused by the vibrations of the pump: suchlike behavior by the free end of the pumping pipe may cause premature wear of said pumping pipe and/or of the pump.
Similar problems are prone to arise in any pipe that is likely to be subjected to forces, notably vibratory loads, in the course of its utilization.